When I get it right, each block in Bitcoins block chain contains a prev hash and a new block hash that includes this prev hash. So the genesis block only has itself and from there on each hash of the prev block is hashed again together with some transactions etc.
So the Merkle tree is in this case a List?

@Edit:
Found out that the Merkle Tree seems not to work globally, it seems to hash all transactions included in a block separately and use them as leaves and then build a binary tree upon them. Where each hash is created over the hash of their children.

So it seems it isn't a special kind of tree and instead a simple binary tree.